If you are getting an error like : Cannot resolve KeyInfo for unwrapping key: KeyInfo 'SecurityKeyIdentifier and your have checked that your certificate is in the right store and right place.
So this might be the reason. check the binding you have...

There are two options:
1. OperationContext.Current.
Pros: This is pretty straightforward and relatively hard to discover.
Cons: This is a thread local storage, and you are invoking a async call, it does not work well.
2. ChannelParameterCollection...